2014 Rocky Mountain Section AAPG Annual Meeting

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Reservoir Characteristics of the Codell Sandstone Tight Oil Play, Northern DJ Basin, Wyoming and Colorado: Extension of Wattenberg into the Oil Window


The Cretaceous Codell Sandstone has been producing gas and oil in the Wattenberg Field in Colorado since 1979. Recent advances in horizontal drilling and multi-stage fracture stimulations have facilitated the extension of the Wattenberg Field into the northern DJ Basin in southeastern Wyoming and northern Colorado, where stabilized production rates up to 1300 BOPD are associated with recently completed horizontal Codell wells. This new play area in Laramie County, Wyoming and northern Weld County, Colorado is thermally in the oil window. Codell Sandstone oil producers have gas-oil ratios less than 2000 scf/bbl. The Codell Sandstone thins from north to south due to erosional truncation beneath an angular unconformity at the base of the Fort Hayes Limestone Member of the Niobrara Formation and ranges from 18 to 33 feet in gross thickness. The Codell Sandstone is a very-fine to fine-grained sandstone and produces oil from two main facies: bioturbated sandstone and laminated sandstone. The laminated facies is parallel to sub-horizontally bedded, has 8 to 15 percent porosity, and .01 to 0.10 millidarcies permeability. The bioturbated sandstone has 8 to 13 percent porosity and .008 to .05 millidarcies permeability. The Codell Sandstone is a low-resistivity pay zone that produces oil with low water cuts from zones with less than 10 ohm-m resistivity. Clay content is 15–25% with abundant microporosity as imaged with epifluorescent microscopy, accounting for high bound water content and explaining the low formation resistivity. Two Codell Sandstone cores provide examples of these facies. The Noble V.O. Child #30–09 core in Laramie County, Wyoming, recovered 25 feet of Codell Sandstone, including 22 feet of bioturbated facies and 3 feet of laminated facies. The Noble Lazy D #03–09 core in Weld County, Colorado, recovered 18.5 feet of Codell Sandstone, including 11 feet of bioturbated facies and 7.5 feet of laminated facies. Core oil saturations and fluorescence under ultraviolet light indicate that the Codell Sandstone is oil saturated in both cores. Nearby horizontal wells drilled and completed in the Codell Sandstone indicate that oil can be recovered economically extending Codell production more than 50 miles north of Wattenberg.